Layer 4 Load Balancing
Load balancing at the transport layer (TCP/UDP) based on IP addresses and ports. Fast because it doesn't inspect packet contents.
What is Layer 4 Load Balancing?
Load balancing at the transport layer (TCP/UDP) based on IP addresses and ports. Fast because it doesn't inspect packet contents.
Layer 4 Load Balancing is a foundational concept that sits in the Load Balancing & Proxies area of system design. Engineers reach for it whenever they need to reason about real-world trade-offs in that space — not just for textbook correctness, but because real production systems at companies like Netflix, Amazon, and Google make these decisions every day.
If you want to go deeper than this definition — with diagrams, code, and a quiz to lock it in — work through the "Layer 4 Load Balancing" lesson linked below. It walks through the why, the mechanism, the trade-offs, and how the giants actually use it in production.
Learn Layer 4 Load Balancing in depth
Full interactive lesson with diagrams, code examples, real-world references, and a quiz.
Open the Layer 4 Load Balancing lessonSee also
Related glossary terms you might want to look up next.
Load Balancer
Distributes incoming traffic across multiple servers so no single server gets overwhelmed. Like a traffic cop directing cars to different lanes.
TCP
A reliable transport protocol that guarantees data arrives in order and without errors. It uses a three-way handshake to establish connections.
Layer 7 Load Balancing
Load balancing at the application layer (HTTP) that can route based on URL paths, headers, cookies, or request content. More flexible but more CPU-intensive.